Relationship Between Bovine Granulosa Cell Apoptosis And Oocyte Developmental Competence: A Study Using The Well In The Drop (WID) System

Oocyte for embryo engineering recovered from ovaries of slaughtered animals have been found highly variable in their quality, so have to be selected strictly. The general methods relied upon the follicle diameter and the morphology of cumulus-oocyte-complexes (COCs), but the accuracy is uncertain. Many studies have showed that follicular atresia caused by granulosa cell apoptosis is associated with the subsequent oocyte developmental competence. But there are many different viewpoints on the relationship between the apoptosis of granulosa cell and the oocyte developmental competence. Therefore, it's necessary to study the assessment of the oocyte quality. In the present study, we succeed to establish the well in the drop system. Under this system we studied the effect of granulosa cell apoptosis on oocyte developmental competence, COCs grades and cumulus expansion. Meanwhile, we studied the feasibility of establishing a new method to estimate the developmental competence of oocyte based on the density of floating granulosa cell in follicle fluid. The results obtained are as follows:1. Hematoxylin assay was used to determinate granulosa cell apoptosis and it was accurate, convenient and cheap.2. The medium volume and density affect maturation quality of oocyte and embryonic development significantly. 10 oocytes per 40μl drop, 25 oocytes per 100μl drop were optimal for IVM. However, too high culture density was proved detrimental to maturation quality of oocyte. Otherwise, it was proved that the medium volume had no impact on maturation quality of oocyte with the same culture density. As to development in vitro, 10 embryos per 40μl drop, 20 embryos per 40μl drop, 25 embryos per...